A growing corpus of research suggests that physical exercise can improve cognition, particularly executive functioning, in older adults. Limitations of existing research, however, have included (a) insufficient attention to the recruitment of sedentary older adults (who would most likely benefit from exercise interventions); (b) insufficient guidance in test selection drawing on neuropsychological theory and practice; (c) failure to elucidate the multiple pathways or components of exercise effects on cognition. Existing research has mostly assumed that exercise effects on cognition are mediated by improvements in underlying cardiovascular and central nervous system fitness. However, exercise also serves as an intervention to improve engagement in complex activity, and may reduce negative affect/depression; these are also possible pathways to cognitive improvement. The current study seeks to better clarify these routes to cognitive improvement via (a) assessment of both potential physical fitness and psychosocial mediators of exercise effects on cognition, and (b) inclusion of a control group that receives a comparable psychoeducational intervention, matched in study contact hours an study-related non-exercise activities, but which does not receive a physical exercise enhancement intervention. Thus, the current proposed study is motivated by the following specific aims: 1. To investigate whether, relative to matched non-exercising control participants, sedentary elders receiving a physical exercise intervention experience improvements in the primary outcome of cognitive function (particularly executive control processes). 2. To determine the separate and joint roles of improvement in proximal outcomes (fitness, activity, and affect) in mediating exercise intervention effects on cognition. The proposed dissertation project is embedded in a larger trial of an exercise-promoting intervention for sedentary older adults. Two randomized groups of 32 adults aged 65+ years will be recruited from the Gainesville/Alachua County, Florida region. Both groups will undergo pre- and post-intervention cognitive, fitness, and psychosocial/socio-emotional assessment. The exercise promotion (experimental) group will receive 16 weeks of intervention (e.g., health and fitness education, weekly peer mentoring and group support session, etc.), while a control/comparison group will receive 16 weeks of "exercise hygiene" instruction, consisting of 16 weeks of comparable education about health and fitness. Statistical analyses will include mixed between-within repeated measures analysis of variance of proximal and primary outcomes, as well as hierarchical/follow-up analyses of covariance, to explore the mediator hypotheses. [unreadable] [unreadable] The proposed research has great relevance to public health, as it examines the effects of a physical exercise intervention on cognitive functioning in a group of older, sedentary adults. Older adults tend to be at increased risk for cardiovascular and associated health problems, including cognitive decline and dementia; interventions such as those proposed herein are critical to reduce the rates of disease and disability in old age. [unreadable] [unreadable] [unreadable]